Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Haptic rendering is the translation of forces in a virtual environment to a physical device that can provide touch-based, a.k.a. haptic, feedback to a user of the haptic rendering device. Both impedance type and admittance type haptic rendering devices are available.
To provide haptic feedback about the virtual environment, objects in the virtual environment are often represented as a collection of polygons, such as triangles, that can be operated upon using a haptic rendering device. The haptic rendering device can be controlled using a “Haptic Interaction Point” (HIP) in the virtual environment, which performs a similar function for the haptic rendering device as a mouse pointer does for a computer mouse. Ideally, the HIP should not be able to penetrate virtual environment objects.
Techniques for six degree-of-freedom (6-DOF) haptic rendering in virtual environments consisting of polygons and/or voxels (volume pixels) have been specified. These efforts are typically divided into direct rendering- and virtual coupling methods where the latter can further be subdivided into penalty-, impulse- and constraint-based methods. The simplest 6-DOF haptic rendering method is the direct method, where the virtual tool perfectly matches the configuration of the haptic rendering device. The force sent to user is directly based on the amount of penetration in the virtual environment. Unfortunately the direct method suffers from problems with “pop through”. Pop through is an artifact that arises when the rendering algorithm erroneously penetrates a thin surface.
In virtual coupling methods, a virtual coupling, or connection, between the haptic rendering device and the virtual tool is utilized. In this method, the force on the haptic rendering device is simply calculated as a spring between the virtual tool, referred to also as ‘god-object’, ‘proxy’ or ‘IHIP’, and the configuration of the haptic rendering device. 6-DOF rendering methods using virtual couplings rely on rigid body simulations, since the virtual tool has to be simulated as a 6-DOF object, as compared to three degree-of-freedom (3-DOF) rendering where the rotational component can be ignored. In penalty-based methods, the configuration (position and rotation) of the virtual tool is calculated using penalty forces based on the tool's penetration depth into objects, similar to how penalty-costs are used in traditional optimization. These penalty forces are then integrated to produce the motion of the virtual tool. This method results in a virtual tool that actually penetrates objects in the environment. Fortunately this penetration is typically very small.
For impulse-based dynamics methods, a virtual object is moved by a series of impulses upon contact/collision (rather than forces based on penetration depth). In constraint-based methods, the virtual tool moves into contact with the environment but (ideally) never violates constraints imposed by the environment.
Many environments can be explored by robots, such as undersea, outer space, and hazardous environments. In some of these environments, robots can be controlled by human operators receiving video and/or audio information from the robot.